Method of resin sealing permanent magnets in laminated rotor core

ABSTRACT

A laminated rotor core ( 36 ) wherein permanent magnets ( 47 ) are inserted in respective magnet insertion holes ( 46 ) is disposed between and pressed by an upper die ( 37 ) and a lower die ( 29 ). The upper die ( 37 ) has resin reservoir pots ( 50 ) provided above the laminated rotor core ( 36 ) and at positions corresponding to the respective magnet insertion holes ( 46 ). Raw resin material put in the resin reservoir pots ( 50 ) is heated by the upper die ( 37 ). Subsequently, the resin material in a liquefied state is ejected from the resin reservoir pots ( 50 ) by plungers ( 52 ) that are inserted and moves vertically in the resin reservoir pots ( 50 ) and is directly filled in the magnet insertion holes ( 46 ). Consequently, the respective magnet insertion holes ( 46 ) are filled with the resin material more evenly and highly reliable products can be supplied at low cost.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.10/584,922, filed on Jun. 29, 2006; which is which is a 371 ofInternational Application No. PCT/JP2006/300910 filed on Jan. 16, 2006,which is based upon and claims the benefit of priority from the priorJapanese Patent Application No. 2005-015860, filed on Jan. 24, 2005, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of resin sealing permanentmagnets in a laminated rotor core, by which the permanent magnetsinserted in a plurality of magnet insertion holes formed in thelaminated core are fixed by injection of resin material into the magnetinsertion holes, the laminated core being formed by stacking a pluralityof core pieces (including a laminated rotor core having a shaft hole ina center thereof).

BACKGROUND ART

Conventionally, a method for fixing permanent magnets to a laminatedcore by resin sealing, such as one disclosed in Japanese PatentApplication Gazette No. 2002-34187, has been known. The inventiondisclosed in the Gazette is constructed as follows. That is, core piecesblanked out by a pressing machine to have prescribed shapes arelaminated and caulked, thereby forming a laminated core having aplurality of magnet insertion holes and resin injection holes locatedcloser to an axis of the laminated core than the magnet insertion holes,both of the holes penetrating in the axial direction through thelaminated core and being in communication with each other viacommunicating grooves. The laminated core thus formed is placed on alower die and a permanent magnet is inserted in each of the magnetinsertion holes. Subsequently, an upper die having inlets matching therespective resin injection holes and a resin supply hole communicatedwith the respective inlets is disposed above the laminated core. Whilethe laminated core is pressed by application of a prescribed pressure onthe upper die, resin material is injected into the resin injection holesof the laminated core from the inlets of the upper die. The resinmaterial ejected from the resin injection holes is filled in the magnetinsertion holes via the communicating grooves, and the resin is curedwhen heated under this condition, thereby fixing the respectivepermanent magnets in the magnet insertion holes of the laminated core.

The conventional method of resin sealing permanent magnets, however, hasthe following problems to be solved.

In filling the magnet insertion holes of the laminated core with theresin material, the resin material is injected into the magnet insertionholes through the resin supply hole and the inlets diverging from theresin supply hole formed in the upper die, and subsequently, through theresin injection holes and the communicating grooves of the laminatedcore. Accordingly, passages of the resin material become long. The longpassages of the resin material require a great amount of resin and makeit difficult to evenly fill the respective magnet insertion holes withthe resin, which causes deterioration in reliability. Furthermore,because of the long passages of the resin, a pump for supplying theresin material is required to have a large supply pressure, and thusequipment becomes expensive.

Furthermore, in the technique disclosed in the above Gazette, thelaminated core is fitted in a recess on the lower die and removed fromthe recess after heating. Such operation requires much time by eithermanual or mechanical means, and is extremely poor in workability.

The present invention has been made in view of the above situations andaims to provide a method of resin sealing permanent magnets in alaminated rotor core, which excels in productivity and workability andis capable of producing highly reliable products at low cost.

DISCLOSURE OF INVENTION

A method of resin sealing permanent magnets in a laminated rotor coreaccording to the present invention for attaining the above objects(hereafter, simply referred to as a method of resin sealing permanentmagnets) comprising: a first step of inserting the permanent magnetsrespectively in a plurality of magnet insertion holes in the laminatedrotor core formed by a stack of a plurality of core pieces; a secondstep of disposing the laminated rotor core between a lower die and anupper die, the lower die being provided for placing the laminated rotorcore thereon, the upper die pairing with the lower die and having resinreservoir pots; a third step of pressing and heating the laminated rotorcore by the upper die and the lower die while heating and liquefying rawresin material put in the resin reservoir pots by the upper die; and afourth step of filling the magnet insertion holes of the laminated rotorcore with the liquefied resin material from the upper die by ejectingthe liquefied resin material from the resin reservoir pots by plungers,the plunger being inserted and moving vertically in the resin reservoirpots.

In the method of resin sealing permanent magnets according to thepresent invention, the filling of the magnet insertion holes with theliquefied resin material in the fourth step means to fill the magnetinsertion holes by injecting the liquefied resin material directly intothe upper ends of the magnet insertion holes from the upper die without,for example, resin injection holes or communicating grooves provided tothe laminated rotor core. The upper die includes members in directcontact with an upper surface of the laminated rotor core (e.g., anupper-die auxiliary block).

In the method of resin sealing permanent magnets according to thepresent invention, it is preferable that the resin reservoir potsprovided in the upper die vertically penetrate the upper die.Accordingly, when the upper die is elevated and detached from the uppersurface of the laminated rotor core after resin sealing of the permanentmagnets in the laminated rotor core, the resin material remained andcured in the resin reservoir pots comes out of the pots and adheres tothe upper surface of the laminated rotor core. This makes cleaning ofthe resin reservoir pots easy. Moreover, the resin material adhered tothe upper surface of the laminated rotor core can be removed with easeby application of load from a horizontal direction.

In the present invention, the resin material may be a thermosettingresin or a thermoplastic resin. When the thermosetting resin is used,the resin needs to be cured by heating the laminated core after beinginjected into the magnet insertion holes. The laminated core ispreferably heated, for example, by heating means provided to the upperand the lower dies.

In the method of resin sealing permanent magnets according to thepresent invention, it is preferable that the laminated rotor core has ashaft hole in a center thereof, and the laminated rotor core is disposedbetween the upper die and the lower die in a state that the laminatedrotor core is placed on a carrier tray having a guide member fitted inthe shaft hole of the laminated rotor core.

Thereby, the laminated core can be precisely positioned on the carriertray and accidents such as falling of the laminated core from thecarrier tray during transportation can be prevented. In consideration ofworkability, the guide member is preferably of a diameterexpandable/shrinkable type, which allows easy centering of a laminatedrotor core formed by e.g., a stack of core pieces not fixed by caulkingor an adhesive agent or a stack of thin core pieces of 0.5 mm or less inthickness having weak caulking strength.

The guide member of a diameter fixed type may also be employed, and inthis instance, it is preferable that an outside diameter of the guidemember is slightly smaller than an inside diameter of the shaft hole ofthe laminated rotor core.

In either case of employing the guide member of the diameterexpandable/shrinkable type or of the diameter fixed type, it ispreferable that the carrier tray is provided with lower vent grooves forrelease of air, the lower vent grooves being respectively incommunication with lower ends of the magnet insertion holes. Thereby,the magnet insertion holes can be stably filled with the resin material.

In the method of resin sealing permanent magnets according to thepresent invention, it is preferable that the filling of the magnetinsertion holes with the liquefied resin material is carried out with adifference in level between an upper end of the laminated rotor core andan upper end of each of the permanent magnets. This prevents protrusionof the permanent magnets from the upper end of the laminated rotor core,and the injected resin material spreads entirely around the permanentmagnets, thereby firmly fixing the permanent magnets. Furthermore, inthis instance, the upper die can be provided with upper vent grooves forrelease of air, the upper vent grooves being respectively incommunication with upper ends of the magnet insertion holes. The uppervent grooves in this instance preferably have an extremely shallow depthto have a configuration that only allows air to be released outside butdoes not allow the resin material to be released outside.

In the method of resin sealing permanent magnets according to thepresent invention, it is preferable that the resin material is athermosetting resin and is thermally cured after being injected into themagnet insertion holes. Because of this, the thermosetting resin willnot melt and the permanent magnets will not move even when the laminatedrotor core is mounted on devices such as a motor and heat is generated.

In the method of resin sealing permanent magnets according to thepresent invention, it is preferable that the resin reservoir pots in theupper die are provided at positions different from those of the magnetinsertion holes as viewed from a top thereof, and the liquefied resinmaterial is supplied to the magnet insertion holes from the resinreservoir pots through resin passages formed on an undersurface of theupper die. In the case where the liquefied resin material is injectedinto the magnet insertion holes through the resin passages formed on theundersurface of the upper die, the resin material filled in the resinpassages remains on the laminated rotor core when the upper die iselevated, and the remaining resin can be peeled off with ease.

In the method of resin sealing permanent magnets according to thepresent invention, it is preferable that the respective resin reservoirpots are provided in an area (region) radially inward of the positionsof the corresponding magnet insertion holes with respect to an axis ofthe laminated rotor core as viewed from a top thereof. In general,because of the structure of the laminated rotor core, the magnetinsertion holes are provided radially outward in the laminated rotorcore, and thus flat parts are formed on an upper surface of thelaminated rotor core between the shaft hole and the magnet insertionholes. Therefore, when the resin reservoir pots are disposed directly onthe flat parts, the flat parts may be utilized as bottoms of the resinreservoir pots.

The laminated rotor core disposed between the upper and the lower diesin the second step is preferably preheated to a prescribed temperature(e.g., about 170° C., more concretely, 165 to 175° C.) by a preheatingunit disposed separately. Moreover, the laminated rotor core disposedbetween the upper and the lower dies is preferably heated by ahigh-frequency induction heating coil, which constitutes a part of aninduction heating means, provided on a side of the laminated rotor coreso that decrease in temperature is prevented as much as possible. Thesetreatments shorten the resin sealing time of the permanent magnets inthe laminated rotor core.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partly omitted front view of a resin sealing apparatus usedin a method of resin sealing permanent magnets in a laminated rotor coreaccording to one embodiment of the present invention.

FIG. 2 is a partly omitted front view of the resin sealing apparatuswith a lower die lowered.

FIG. 3 is a plan view of the laminated rotor core shown overlapped withresin reservoir pots and resin passages connected to the pots.

FIG. 4 is a front view showing an entire structure of the resin sealingapparatus.

FIG. 5 is a partly omitted side view showing the lower die of the resinsealing apparatus and the vicinity thereof.

FIG. 6 is a plan view of a middle stationary plate used in the resinsealing apparatus.

FIG. 7 (A) and (B) are plan views of a holder guide and a plungerholder, respectively.

FIG. 8 is an explanatory diagram of the method of resin sealingpermanent magnets in a laminated rotor core using the resin sealingapparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, referring to the accompanying drawings, one embodiment of thepresent invention is explained. First, a resin sealing apparatus used toimplement a method of resin sealing permanent magnets in a laminatedrotor core according to the one embodiment of the present invention isexplained.

As shown in FIG. 4, a resin sealing apparatus 10 includes a mount 14having four column members 13 whose upper sides and lower sides arerespectively coupled by upper and lower coupling members 11, 12; fourguideposts 15 provided inside the mount 14, each of the guideposts 15being fixed to upper and lower sides of the mount 14 to stand upright; alower stationary member 16 fixed to lower portions of the guideposts 15;a lower-die support member 17 vertically movably disposed in middleportions of the guideposts 15; and a worm jack 18 which is one exampleof a lifting means for lifting and lowering the lower-die support member17.

Four corners of the lower-die support member 17 are fixed by slidingbearings 19 which are vertically movably attached to the respective fourguideposts 15 having a circular cross section. As shown in FIGS. 1 and2, the respective sliding bearings 19 have bearing metals 20, 21provided therein to move up and down smoothly on the guideposts 15.

The worm jack 18 is driven by a servomotor 22. A vertically movableoutput shaft 23 of the worm jack 18 is coupled to the lower-die supportmember 17 via a vertically movable support member 24, a plurality ofdisc springs 25 for reducing impact load, a middle plate 26, and a loadcell 27 which is one example of load sensors. Accordingly, the worm jack18 allows the lower-die support member 17 to move up and down along withthe support member 24, the plurality of disc springs 25, the middleplate 26 and the load cell 27.

A lower die 29 is placed over the lower-die support member 17 via a heatinsulating plate 28. As shown in FIG. 5, the lower die 29 and the heatinsulating plate 28 are detachably fixed on the lower-die support member17 by attachment fittings 30. A plurality of grooves 31 are provided inthe lower die 29, and a roller 32 is disposed in each upper portion ofthe grooves 31 in such a manner that a mounting shaft 33 of the roller32 is pressed from below by a spring 34. The rollers 32 are partlyprotruded from an upper surface of the lower die 29 in a natural state,and allow a carrier tray 35 on which a laminated rotor core 36 is placedto roll and move on the lower die 29. A heater not shown which is oneexample of a heating means is provided inside the lower die 29 to heatthe laminated rotor core 36 placed on the carrier tray 35. As shown inFIGS. 5 and 1, strength of the springs 34 is adjusted so that thesprings 34 are shrunk to bring the carrier tray 35 on which thelaminated rotor core 36 is placed into contact with the lower die 29when the lower die 29 is elevated by operating the worm jack 18 and anupper end of the laminated rotor core 36 is brought into contact with anupper-die auxiliary block 38, i.e., a part of an upper die 37 locatedover the laminated rotor core 36. A distal end of a guide member 43projecting from the upper end of the laminated rotor core 36 is to beinserted in a depression 38 a which is formed in a central bottomportion of the upper-die auxiliary block 38.

As shown in FIGS. 1, 2 and 4, guide rods 39 penetrate four cornerportions of the lower die 29, the heat insulating plate 28 and thelower-die support member 17. Air cylinders 40 provided in the supportmember 24 are respectively disposed at lower ends of the guide rods 39.If necessary, the guide rods 39 are elevated to support the upper die37.

As shown in FIG. 5, the attachment fittings 30 are disposed at bothsides in a horizontal direction, i.e., width direction (X-X′ direction)of both end portions in an anteroposterior direction (Y-Y′ direction) ofthe lower die 29 to fix the lower die 29 to the lower-die support member17. The attachment fittings 30 are not shown in FIGS. 1, 2 and 4.

The carrier tray 35 is provided to hold the laminated rotor core 36, andincludes a receiving plate 42, each side of which is longer than anoutside diameter of the laminated rotor core 36, and the guide member 43provided in a center of the receiving plate 42. The guide member 43 hasa diameter that expands or shrinks slightly by an elastic member notshown such as a spring, a total length slightly longer (e.g., by about 1to 5 mm) than that of the laminated rotor core 36, and an upper endportion processed to be in a conical shape (i.e., a periphery of theupper end portion chamfered). Having such structure, the guide member 43can be easily inserted in a shaft hole 41 of the laminated rotor core36. As shown in FIG. 3, mutually facing projections 44 for stoppingrotation are formed inside the shaft hole 41 of the laminated rotor core36. Alternatively, the guide member 43 may be of a diameter fixed type.In this case, it is preferable that an outside diameter of the guidemember 43 is slightly less (e.g., by 2 to 30 μm) than an inside diameterof the shaft hole 41 of the laminated rotor core 36.

As shown in FIGS. 1 and 2, the laminated rotor core 36, which isproduced by laminating a predetermined number of core pieces previouslyblanked out by a pressing machine (not shown) having a well-knownstructure, is placed on the carrier tray 35. Immediately above thelaminated rotor core 36, there are provided an upper-die main body 45which is a part of the above-described upper die 37, and the upper-dieauxiliary block 38 (also called as a cavity block) which is screwed ontoa lower portion of the upper-die main body 45 and is slightly smallerthan the upper-die main body 45 in width. As shown in FIG. 3, thelaminated rotor core 36 has a plurality (eight in the presentembodiment) of magnet insertion holes 46 having a rectangular crosssection provided in an outer peripheral portion thereof, and permanentmagnets 47 having cross-sectional dimensions slightly smaller (e.g., by20 to 500 μm per side) than those of the magnet insertion holes 46 areinserted in the magnet insertion holes 46, respectively.

As shown in a partly enlarged view of FIG. 1 and by a double-dot-dashedline in FIG. 3, the upper die 37 placed immediately above the laminatedrotor core 36 includes resin reservoir pots 50 circular in cross sectionrespectively corresponding to the magnet insertion holes 46, and resinpassages 51 (generally called as runners) respectively connected to theresin reservoir pots 50 for leading a liquefied resin material from thepots 50 to the magnet insertion holes 46. Each of the resin reservoirpots 50 penetrates the upper-die main body 45 and the upper-dieauxiliary block 38 which are vertically stacked to constitute the upperdie 37. The each of the resin reservoir pots 50 of the upper-die mainbody 45 is provided with a bushing 53 to reduce friction with avertically moving plunger 52 inserted in the each of the pots 50. Aheater not shown, which is one example of a heating means, is installedin the upper-die main body 45. The heater heats and melts raw materialof the resin material (a thermosetting resin, more specifically an epoxyresin, is used in the present embodiment) in a tablet form put into theresin reservoir pots 50 from above. After the liquefied resin materialis injected into the magnet insertion holes 46 of the laminated rotorcore 36, the heater further heats the laminated rotor core 36 to curethe resin material. The resin reservoir pots 50 vertically penetrate theupper die 37, i.e., to a lower end of the upper-die auxiliary block 38,and the resin passages 51 are provided in the upper-die auxiliary block38.

Stopper mechanisms 55 for fixing the upper die 37 to the guideposts 15at a predetermined height are respectively provided on the guideposts15. Each of the stopper mechanisms 55 includes a stopper rod 56, apneumatic cylinder 57 for advancing and withdrawing the stopper rod 56,and an attachment fitting 58 for fixing a guide member of the stopperrod 56 and the pneumatic cylinder 57 to the each guidepost 15. Advancelimit of the mutually facing stopper rods 56 is set, as shown in FIG. 1,so that intervals between distal ends of the stopper rods 56 at bothsides become shorter than a width of the upper-die main body 45 butlonger than a width of the upper-die auxiliary block 38. According tothe structure, the upper die 37 in the upper limit position can beprevented from moving downward by activating the stopper mechanisms 55.

As shown in FIG. 2, a middle stationary plate 62 is provided over theupper die 37. The middle stationary plate 62 is supported by fourhanging fittings 61 at both sides whose upper ends are respectivelyfixed by bolts 63 to a lower portion of an upper stationary plate 59 viaa heat insulating plate 60. The upper stationary plate 59 is a part ofthe upper coupling member 11, and couples upper potions of the fourguideposts 15. Namely, the middle stationary plate 62 is held atpredetermined height in a state that both end portions thereof arefitted in engagement grooves 64 comprising cutouts formed respectivelyin middle portions of the hanging fittings 61. Heat insulating plates 65are respectively provided on outer sides of the hanging fittings 61.

FIG. 6 shows the details of the middle stationary plate 62 having asubstantially rectangular shape when viewed from a top thereof, andradially disposed cutouts 67 are respectively formed on four corners ofthe middle stationary plate 62. Vertical guides 66 having a rectangularcross-section and vertically disposed on the four corners of the upperdie 37 are vertically movably inserted in the cutouts 67. In a centralposition of the middle stationary plate 62, there are provided plungerguide holes 68 precisely conforming to the respective eight resinreservoir pots 50 formed in the upper die 37. In the middle stationaryplate 62, through-holes 70 having a circular cross section are providedradially outward of the plunger guide holes 68. Four guide tubes 69 forpositioning which are vertically disposed on the upper die 37 penetratethe through-holes 70. The four guide tubes 69 respectively have stopperflanges 71 provided in upper portions thereof, and are fixed to theupper-die main body 45 constituting the upper die 37 by long bolts 72.

Spring insertion holes 73 are disposed between each of front and rearpairs of the through-holes 70 disposed at both sides in the X-X′direction of the middle stationary plate 62. Coil springs 75 are fixedto an upper potion of the upper-die main body 45 by guide rods 74 whoselower portions are screwed to the upper-die main body 45, and insertedin the spring insertion holes 73 with sufficient clearance between thecoil springs 75 and the holes 73. Spring retaining caps 77 for retainingupper ends of the coil springs 75, in which upper potions of the coilsprings 75 are inserted, are disposed over the respective springinsertion holes 73. Accordingly, the coil springs 75 in a shrunken stateare housed in the spring insertion holes 73 and the spring retainingcaps 77, thereby allowing the elevated upper-die main body 45 to comeinto close contact with the middle stationary plate 62. As shown in FIG.2, when the lower-die support member 17 is lowered by operating the wormjack 18, space G is formed between the upper die 37 and the middlestationary plate 62. Thus, the raw resin material (generally in a tabletform) can be put in the resin reservoir pots 50 by a material supplyunit not shown or by manual.

A concave portion 78 for alignment is provided in a lower centralportion of the middle stationary plate 62, and precisely matches aconvex portion 79 for alignment provided in a central portion of anupper surface of the upper-die main body 45. Accordingly, the plungerguide holes 68 and the resin reservoir pots 50 are precisely aligned.

A plunger holder 81 for supporting the plungers 52 which force the resinmaterial out of the eight resin reservoir pots 50 is provided over themiddle stationary plate 62. As shown in FIGS. 1 and 4, the plungerholder 81 is connected via a coupling mechanism 84 to a shank 85 drivenup and down by a warm jack 83 i.e., one example of a lifting means, andthe plunger holder 81 can be elevated and lowered by operation of theworm jack 83. A cylindrical holder guide 86 for guiding the plungerholder 81 is fixed on the middle stationary plate 62.

As shown in FIGS. 7 (A) and (B), the holder guide 86 has a plurality ofprojections 87 inside, and the plunger holder 81 has guide grooves 88 inwhich the projections 87 are inserted. The plunger holder 81 has anoutside diameter less than an inside diameter of a portion of the holderguide 86 excluding the projections 87 so that the plunger holder 81expanded in diameter by thermal expansion does not interfere with theinside of the holder guide 86. The plunger holder 81 and the holderguide 86 are aligned by inserting the projections 87 of the holder guide86 in the guide grooves 88 of the plunger holder 81.

The eight plungers 52 are perpendicularly attached to the plunger holder81 by a screw connection, and can be replaced if necessary. Numerals 89in FIG. 7 (B) show female screws in which the plungers 52 are screwed.

A horizontal guide plate 91 is secured right below the upper stationaryplate 59 through the heat insulating plate 60 by screws not shown.Spacing plates 93, 94 which are movable in the horizontal direction(X-X′ direction) centering the shank 85 are disposed between thehorizontal guide plate 91 and the upper end of the holder guide 86. Thecoupling mechanism 84 for connecting the shank 85 and the plunger holder81 includes an engaging portion 92 formed in a lower portion of theshank 85, an auxiliary plate 95 fixed to an upper portion of the plungerholder 81 and having the same planar shape as that of the plunger holder81, and a connecting portion 96 fixedly secured to the auxiliary plate95 and engaged with the engaging portion 92. The engaging portion 92comprises an annular groove provided in the lower portion of the shank85, and the connecting potion 96 comprises a fitting having a horseshoeinner projection to be fitted in the annular groove from a specifieddirection (for example, the horizontal direction). When fixing of theauxiliary plate 95 to the plunger holder 81 is released and theauxiliary plate 95 is pulled in a specified outward direction with thespacing plates 93, 94 pulled outward, the plunger holder 81 can beseparated from the shank 85.

As shown in FIGS. 1, 2 and 7 (B), 16 protruding pins 81 a are disposedin the periphery of the plunger holder 81, and the auxiliary plate 95prevents upper ends of the protruding pins 81 a from coming out of theplunger holder 81 upward. The protruding pins 81 a thus fixed to theplunger holder 81 penetrate pin through-holes 62 a of the middlestationary plate 62 as shown in FIG. 6 and through-holes provided in theupper die 37, thereby pressing the upper end portion of the laminatedrotor core 36 located immediately below the upper die 37. Such structureallows the laminated rotor core 36 which is finally resin-sealed to bedetached from the upper die 37 (the upper-die auxiliary block 38 inparticular).

As shown in FIG. 4, the shank 85 vertically movably penetrates a centerof the upper stationary plate 59 via a sliding bearing 97, and the wormjack 83 secured by a support member 98 is connected to an upper end ofthe shank 85. The worm jack 83 is driven by a servomotor 100 sustainedby a support member 99.

Next, with reference to FIGS. 1 to 4, the method of resin sealingpermanent magnets in a laminated rotor core according to the oneembodiment of the present invention using the resin sealing apparatus 10is explained following procedures shown in FIG. 8 (a) to (i).

(a) The predetermined number of core pieces having a predetermined shape(as shown in FIG. 3) are laminated to produce the laminated rotor core36 having the plurality (eight in the present embodiment) of the magnetinsertion holes 46 formed in the periphery thereof. The laminated rotorcore 36 is placed on the carrier tray 35, and the prescribed permanentmagnets 47 are put respectively into the magnet insertion holes 46. Thelaminated rotor core 36 set on the carrier tray 35 is placed on thelower die 29 by a conveying means etc. not shown, and an axis of thelaminated rotor core 36 is aligned with that of the upper die 37.(Supply of the laminated rotor core)

Preferably, the laminated rotor core 36 is preheated to, for example,around 170° C. by a preheating unit (for example, a heating furnace)equipped in the previous step.

(b) The worm jack 18 is driven to slightly elevate the lower-die supportmember 17, the lower die 29 and the laminated rotor core 36 placedthereon, thereby bringing the laminated rotor core 36 into close contactwith the upper die 37. More specifically, the laminated rotor core 36comes into contact with an undersurface of the upper-die auxiliary block38, and the distal end of the guide member 43 protruding from a centralportion of the upper surface of the laminated rotor core 36 is fitted inthe depression 38 a provided in a central portion of a lower portion ofthe upper-die auxiliary block 38. At this point, since the space G(about 80 mm high in the embodiment) exists between the upper die 37 andthe middle stationary plate 62, the raw material of the thermosettingresin in a predetermined amount (having a tablet form) is put in therespective eight resin reservoir pots 50 having openings at upperportions thereof. Here, the supply of the raw material (raw resinmaterial) may be carried out automatically or manually. Then, the resinmaterial is heated to a temperature in the vicinity of some 170° C. bythe heater installed in the upper die 37. (Supply of the tablets)

(c) When viscosity of the resin material is reduced by heating, thelower die 29 is elevated by the worm jack 18 via the lower-die supportmember 17 so that the laminated rotor core 36 set on the carrier tray 35is pressed against the upper die 37. Accordingly, the space G betweenthe upper die 37 and the middle stationary plate 62 becomes null.Moreover, the convex portion 79 for alignment provided in the upperportion of the upper die 37 fits in the concave portion 78 formed in thelower portion of the middle stationary plate 62, and the eight plungerguide holes 68 formed in the middle stationary plate 62 are alignedrespectively with the eight resin reservoir pots 50 provided in theupper die 37.

Next, when the worm jack 83 in the upper potion of the resin sealingapparatus 10 is driven to lower the plunger holder 81, the eightplungers 52 push the melted resin material (i.e., the thermosettingresin) out of the resin reservoir pots 50, thereby filling therespective magnet insertion holes 46 with the resin material through theresin passages 51.

The heaters in the lower and the upper dies 29, 37 are operated to heatthe laminated rotor core 36 at a temperature in the vicinity of about170° C. for three minutes. This enables curing of the thermosettingresin and fixing of the permanent magnets 47 in the magnet insertionholes 46. In this instance, since the permanent magnets 47 are insertedin the magnet insertion holes 46 with the lower surfaces of the magnets47 coincided with the lower edges of the holes 46, there is a slightdifference in level (e.g., 2 to 20 μm) between an upper end of thelaminated rotor core 36 and an upper end of the each permanent magnet47. Thus, none of top portions of the permanent magnets 47 project fromthe magnet insertion holes 46, which ensures contact of the uppersurface of the laminated rotor core 36 with the upper die 37.Furthermore, the resin material passes through space formed between theupper die 37 and the top portions of the permanent magnets 47, whichallows more efficient filling of the magnet insertion holes 46 with theresin material.

Air inside the magnet insertion holes 46 is released outside throughupper vent grooves and lower vent grooves for release of airrespectively provided on a lower surface of the upper-die auxiliaryblock 38 and on a surface of the receiving plate 42 of the carrier tray35. The upper and lower vent grooves have such depth (e.g., 0.2 to 0.6μm) that allows passage of air but not of the resin material. In thismanner, the material of the thermosetting resin is once liquefied byheating, and the resin is filled in the magnet insertion holes 46 fromthe upper surface of the laminated rotor core 36 via the resin passages51. As a result, the thermosetting resin is easily put into the magnetinsertion holes 46. (Die clamping and resin injection)

(d) Next, as shown in FIG. 1, the stopper mechanisms 55 are actuated toproject the four stopper rods 56 so that the stopper rods 56 are broughtinto contact with lower surfaces of both end portions in the horizontaldirection of the upper-die main body 45 in its upper limit position,thereby preventing lowering of the upper die 37. The plunger holder 81is further pushed downward (e.g., 5 mm) by the worm jack 83 in thisstate, and the protruding pins 81 a are lowered and protruded from thelower end of the upper die 37 to push and detach the laminated rotorcore 36 from the upper die 37. As a result, the laminated rotor core 36is separated from the upper die 37. The resin material remained andcured in the resin reservoir pots 50 of the upper die 37 adheres to theupper surface of the laminated rotor core 36, and thereby lower portionsof the resin reservoir pots 50 become empty. (Die opening)

Then, the carrier tray 35 on which the laminated rotor core 36 is placedis detached from the lower die 29, the laminated rotor core 36 isremoved from the carrier tray 35, and the carrier tray 35 is conveyed toa subsequent step by a separately arranged conveying means. The resinmaterial remained in the resin reservoir pots 50 and the resin passages51 is cured and adhered to the upper portion of the laminated rotor core36. However, the unwanted resin material can be easily removed becausethe resin passages 51 are narrow, namely, a cross sectional area of theresin passages 51 is small.

(e) The plungers 52 and the resin reservoir pots 50 are cleaned with acleaner 101 having a brush. (Cleaning of the plungers) Since the resinreservoir pots 50 are empty, cleaning can be carried out easily.

(f) The lower die 29 is elevated by the worm jack 18 via the lower-diesupport member 17, and at the same time, the air cylinders 40 are drivento elevate the guide rods 39 so that upper ends of the four guide rods39 support the upper die 37.

(Preparation of Upper Die Opening)

(g) After the stopper mechanisms 55 are operated to withdraw the fourstopper rods 56, the lower die 29 is lowered by the worm jack 18 via theupper-die support member 17, and at the same time, the upper die 37 islowered along the guide tubes 69 to be in the initial position (seeFIGS. 1 and 2). Then, the lower die 29 is further lowered. (Die opening)

(h) The air cylinders 40 are actuated to lower the four guide rods 39,and the space G between the middle stationary plate 62 and the upper die37 is cleaned with a cleaner 102 having a brush. (Cleaning of tabletinput portions)

(i) The upper die 37 and the lower die 29 are cleaned with a cleaner 103having upper and lower brushes. (Cleaning of the dies)

Implementation of the present invention is not limited to the aboveembodiment, and various modifications may be made without departing fromthe scope or sprit of the present invention. Therefore, the presentinvention includes any method of resin sealing permanent magnets in alaminated rotor core according to present invention embodied by thecombination of a part or all of the above embodiment and modifications.For example, in the present embodiment, the upper die 37 is constitutedby the separate upper-die auxiliary block 38 and upper-die main body 45.Alternatively, the upper die 37 may be constituted by one member.

In the present embodiment, the eight magnet insertion holes 46 areprovided in the laminated rotor core 36. Alternatively, a differentnumber of the magnet insertion holes 46 may be provided.

Moreover, in the present embodiment, the resin reservoir pots 50 areprovided in positions respectively corresponding to the magnet insertionholes 46 of the laminated rotor core 36 and radially inward with respectto the magnet insertion holes 46. However, the present inventionincludes a case where the resin reservoir pots are provided immediatelyover the magnet insertion holes or the resin reservoir pots partlyoverlap the magnet insertion holes.

In the present invention, the vent grooves are formed on the uppersurface of the receiving plate 42 of the carrier tray 35 and theundersurface of the upper-die auxiliary block 38, both of which come indirect contact with the laminated rotor core 36. Alternatively, the ventgrooves on either one or both of the receiving plate 42 and theupper-die auxiliary block 38 may be omitted if required.

In the present embodiment, the respective plungers 52 are screwed to theplunger holder 81 directly. Alternatively, springs may be provided inintermediate positions of the respective plungers 52.

Although the thermosetting resin is used as the resin material in thepresent embodiment, the present invention is not limited thereto.Alternatively, a thermoplastic resin may be used when the laminatedrotor core is used in a motor with a low heat generation.

Furthermore in the present invention, an induction heating coil may bedisposed in the vicinity of the laminated rotor core 36 placed betweenthe lower and upper dies 29, 37, and electric power is supplied to theinduction heating coil from a high-frequency power source installedseparately, thereby heating the laminated rotor core 36. This enablesreduction in time of resin sealing the permanent magnets in thelaminated rotor core. The induction heating coil and the high-frequencypower source constitute an induction heating means.

INDUSTRIAL APPLICABILITY

As evidenced by the above explanation, in the method of resin sealingpermanent magnets in a laminated rotor core according to the presentinvention, the upper die is brought into contact with the magnetinsertion holes provided in the laminated rotor core, and the resinmaterial is filled in the magnet insertion holes directly from specifiedresin reservoir pots provided in the upper die. Thus, the respectivemagnet insertion holes can be filled with the resin material evenly, andaccordingly highly reliable products can be provided.

Furthermore, since it is not necessary to put the resin material intoextra portions of the laminated rotor core, waste of the resin materialcan be reduced. As a result, utilization efficiency of the core isimproved, and more efficient motors or generators can be provided.

Particularly, in a case the resin reservoir pots provided in the upperdie vertically penetrate the upper die, the resin material can beinjected into the magnet insertion holes directly by putting the resinmaterial in the resin reservoir pots, melting, and pressing the resinmaterial by the plungers. After the resin material is cured, the resinmaterial remained in the resin reservoir pots can be removed with easeby detaching the upper die from the laminated rotor core.

1. A method of resin sealing permanent magnets in a laminated rotor corecomprising: a first step of inserting the permanent magnets respectivelyin a plurality of magnet insertion holes in the laminated rotor coreformed by a stack of a plurality of core pieces; a second step ofdisposing the laminated rotor core between a lower die and an upper die,the lower die being provided for placing the laminated rotor corethereon, the upper die pairing with the lower die and having resinreservoir pots; a third step of pressing and heating the laminated rotorcore by the upper die and the lower die while heating and liquefying rawresin material put in the resin reservoir pots by the upper die; and afourth step of filling the magnet insertion holes of the laminated rotorcore with the liquefied resin material from the upper die by ejectingthe liquefied resin material from the resin reservoir pots by plungers,the plunger being inserted and moving vertically in the resin reservoirpots, wherein the resin reservoir pots provided in the upper dievertically penetrate the upper die, and wherein the resin reservoir potsin the upper die are provided immediately over the magnet insertionholes or the resin reservoir pots partly overlap the magnet insertionholes as viewed from a top thereof, and the liquefied resin material issupplied to the magnet insertion holes from the resin reservoir pots. 2.The method of resin sealing permanent magnets in a laminated rotor coreas defined in claim 1, wherein the laminated rotor core has a shaft holein a center thereof, and the laminated rotor core is disposed betweenthe upper die and the lower die in a state that the laminated rotor coreis placed on a carrier tray having a guide member fitted in the shafthole of the laminated rotor core.
 3. The method of resin sealingpermanent magnets in a laminated rotor core as defined in claim 2,wherein the carrier tray is provided with lower vent grooves for releaseof air, the lower vent grooves being respectively in communication withlower ends of the magnet insertion holes.
 4. The method of resin sealingpermanent magnets in a laminated rotor core as defined in claim 1,wherein the filling of the magnet insertion holes with the liquefiedresin material is carried out with a difference in level between anupper end of the laminated rotor core and an upper end of each of thepermanent magnets.
 5. The method of resin sealing permanent magnets in alaminated rotor core as defined in claim 1, wherein the laminated rotorcore disposed between the upper die and the lower die in the second stepis preheated.
 6. The method of resin sealing permanent magnets in alaminated rotor core as defined in claim 1, wherein the laminated rotorcore mounted on the lower die is heated from outside by an inductionheating means.